The Conservatives have dropped 3% to 29% in the latest Observer/Opinium poll at the same time as Ukip have surged by the same amount to 13% – a record for the anti-EU party since Opinium surveys began in 2008.

While the Labour party increased its lead over the Tories by two points to 9%, it too fell, by just 1%, to 38%.

The Lib Dems were four points adrift of Ukip, though Nick Clegg's party was up 1% on a fortnight ago, at 9%.

The Ukip surge will worry the Tories in particular, as it appears to have had a direct effect on Conservative support.

Ahead of the autumn statement on Wednesday by the chancellor, George Osborne, voters were asked if they believed the government should concentrate most on cutting the deficit or on stimulating growth. Forty three per cent thought growth promotion was preferable even if this meant increasing borrowing, while 33% thought ministers should continue to focus more on reducing the deficit by lowering spending.

Fifty three per cent of voters said cuts to welfare had gone far enough while 29% thought they should continue. Some 72% of Labour voters believed welfare had suffered enough, compared with 31% of Conservatives.

Cutting the deficit was more popular among male voters (39% of whom supported it, over focusing on growth) than among female voters where support was 27%.

Opinium carried out an online survey of 1,949 GB adults aged 18+ from 27 to 29 November 2012. Results have been weighted to nationally representative criteria.

• This article was amended on 2 December 2012. The original incorrectly said Opinium surveys began in 2011, rather than the correct date of 2008.